Producing oil from nuclear-produced chimneys in oil shale



July 8, 1969 H. w. PARKER 3,454,958

PHODUCING OIL FROM NUCLEAR-PRODUCED CHIMNEYS IN OIL SHALE Filed Nov. 4, 1966 COMPRESSOR' EXCESS GAS 40 ALTERNATE MINED CON DUIT O0 BETWEEN 0 0 HOTEcooL O00 00 sHALE V000 cooL. 00 00000 0 0 02m ogaidqm@ 280@ 26 INVENTOR.

H.W. PARKER bi1) 7V BoUNDARYf) United States Patent Ofce 3,454,958 Patented July 8, 1969 3,454,958 PRODUCING OIL FROM NUCLEAR-PRODUCED CHIMNEYS IN OIL SHALE Harry W. Parker, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Filed Nov. 4, 1966, Ser. No. 592,080 Int. Cl. E21b 43/00 U.S. Cl. 166--256 10 Claims ABSTRACT OF THE DISCLOSURE Oil is produced from first and second spaced-apart explosion chimneys in an oil shale by passing a zone of heat through the shale in the first chimney to heat said shale to a temperature of at least 800 F. under conditions to leave a hot residue containing sufficient coke to support in situ combustion. A gas comprising air is then passed upward through the first chimney to burn the coke therein and provide a hot retorting gas which is passed downwardly through the shale in said second chimney so as to produce oil in the bottom thereof. The produced oil and efliuent gas from said second chimney are separately recovered and said efiiuent gas is recycled to said first chimney as a part of the gas passed upwardly therethrough.

This invention relates to a process for the in situ production of oil, with hot gases from broken shale in nuclear chimneys formed in oil shale.

The in situ retorting of shattered or broken oil shale in nuclear chimneys produced by positioning a nuclear explosive device in the shale and actuating the device is disclosed by M. A. Lekas and N. C. Carpenter in an article entitled Fracturing Oil Shale with Nuclear Explosives for In-Situ Retorting presented in the Quarterly of the Colorado School of Mines, volume 60, No. 3, I uly 1965, pp. 7-30. The nuclear chimney in an oil shale is a highly permeable mass of broken and displaced shale ranging in size from blocks 2 to 3 feet across to sand-size grains. A 250 kiloton explosive device set off in a thick shale formation is estimated to create a collapse chimney 400 feet in diameter and 1000 feet high. The permeability of the chimney shale makes it feasible to produce oil therefrom in situ with hot gas at a temperature of at least 800 F. or by in situ combustion of a portton of the shale oil or kerogen in the shale and driving out another portion with resulting heat and hot gases. One of the problems encountered in retorting and production by in situ combustion is channeling of air or hot retorting gases which result in bypassing substantial areas of the chimney shale.

This invention is concerned with an improved method of in situ production of oil from nuclear chimney oil shale with hot gases which reduces cha-nneling.

Accordingly, it is an object of the invention to provide an improved process for the in situ retorting and production of oil shale in a nuclear chimney. Another object is to provide a process for the in situ production of oil from nuclear chimney oil shale which decreases channeling of gases within the nuclear chimney. A further object is to provide such a process which makes more economical use of retorting gases than heretofore. Other objects of the invention will become apparent to one skilled in the art upon consideration of the accompanying disclosure.

A broad aspect of the invention, as applied to first and second spaced-apart explosion chimneys in a subterranean oil shale, comprises heating the shale to a temperature of at least 800 F. to produce oil therefrom, leaving a hot residue containing sufficient coke to support in situ combustion; thereafter, passing a gas comprising air and recycled retorting gas upwardly thru the first chimney so as to heat. said gas to a. temperature of at least 800 F.;

passing the resulting hot retorting gas from the first chimney downwardly thru the shale in the second chimney so as to produce liquid oil from the bottom thereof; separately recovering liquid oil and eiuent gas from the bottom of the second chimney; and recycling a substantial portion of the recovered efliuent gas to the stream of ga-s introduced to the first chimney.

Thus, according to the invention, there is provided a process for producing oil from first and second spacedapart explosion chimneys in an oil shale which comprises, in combination, the steps of: (a) producing oil from said first chimney by heating the shale therein to a temperature of at least 800 F. by passing a zone of heat downwardly from the top section to the bottom section of said chimney unider conditions leaving a hot residue containing sufficlent coke to support in situ combustion; (b) thereafter, passing a gas comprising air and recycled retorting gas upwardly thru the hot residue in said first chimney to burn said coke and extract heat from said residue, providinga hot retorting gas at a temperature of at least 800 F.'as an effluent; (c) passing hot retorting gas of step (b) downwardly thru the shale in said second chimney so as to produce liquid oil in the bottom thereof; (d) separately recovering produced oil and efiiuent gas from the bottom section of the chimney of step (c); and (e) recycling a ,The first chimney may be produced by any one of three y methods as: (1) reverse in situ combustion from the top of'the chimney to the bottom thereof; (2) direct drive combustion from the top of the first chimney to the bottom thereof with only a sufiicient air concentration to control the burning rate at a temperature in the range of about 900 to 1200 F. so as to leave a coke deposit, the burning rate being controlled by mixing combustion gas with air at a volume ratio of combustion gas to air in the range of about 3:1 to 5:1; and (3) by retorting with hot combustion gas forced downwardly thru the first chimney with hot oil being recovered from the bottom of the chimney.

At the end of the production of oil from the first chimney, the spent shale therein is at a temperature substantially above 800 F. The instant process transfers most of this heat to the second chimney so that supplementing the transferred heat with heat produced by burning residual coke in the first chimney provides adequate heat supply for producing oil from the shale in the second chimney (assuming that the volumes of lchimney shale ini'the two chimneys are approximately the same). It is more economical to produce shale oil from the shale aggregates in the chimneys without burning a portion of the shale to provide the heat for retorting. Thus, while a portion of the shale oil in the first chimney is burned to supplement the heat transferred to the second chimney, the second chimney is produced substantially entirely without combustion of any of the oil in the shale aggregates there- A more complete understanding of the invention may be had by reference to the accompanying schematic drawing which is an elevation in partial section thru an oil shale 10 containing a pair of nuclear chimneys 12 and 14 spaced apart a short distance. A shaft or drill hole 16 communicates with the upper end of chimney 12 while a second shaft or drill hole 18 communicates with the upper end of chimney 14. A valve crossover line 20 connects drill holes 16 and 18. Wells 22 and 24 are drilled adjacent chimneys 12 and 14, respectively, and these wells are connected with their respective chimneys via tunnels 26 and 28, respectively, formed in conventional manner. Well 24 is provided with a tubing string 30 equipped with a -pump 32 on the lower end therof and leads to an oil production line 34. A valved crossover line 36 connects well 22 with well 24 and is provided with a compressor- 38. Line 40 connects with well 24 and serves to remove excess gas from this well. Air line 42 connects with well 22 for injection of air for in situ combustion purposes in chimney 12. Line 44 connects with drill hole 16 for introducing air or hot combustion gas for producing oil from chimney 12 in the initial stages of the process. An alternate ow path from top of chimney 12 to the top of chimney 14 may be provided by drilled or mined tunnel 46.

At the stage of the process illustrated in the drawing, the .broken shale in chimney 12 has been produced by the selected method and air from line 42 is being mixed with retorting gas recycled from well 24 via line 36 under the impetus of compressor 38, and the boundary between the hot and cool shale in chimney 12 is adv'icing upwardly from the level 48 shown in the chimney. The resulting hot retorting gas vented thru drill hole 16 is passed thru line 20 into drill hole 18 from which it passes downwardly thru chimney 14 advancing boundary 50 between the hot spent shale and the cool unspent shale toward the bottom of chimney 14.

In order to produce oil from shale in chimney 12 by inverse drive in situ combustion, the shale in the tOp of chimney 12 is ignited by any suitable means to establish a combustion zone across the bed of shale in the chimney. The combustion zone may be established by burning a bed of charcoal soaked in a suitable fuel, lsuch as diesel oil, and injecting air thru line 44 or thru line 42 so as to force air thru the shale bed into the charcoal which is ignited by a fuse or other similar deviceg" or an autoignitable fuel, such as tung oil or linseed il, alone, or admixed with diesel oil, or similar heavy oil, may be positioned in or on the top of the shale bed and air fed thereto either thru well 22 and the shale bed or thru drill hole 16 until the combustion zone is `well established, after which it is essential to feed air"thru the bed from well 22 to cause the resulting combustion zone or front to progress or advance downwardly countercurrently to the air to the lower section of the betl of shale. Continued air injection as the combustion z'one reaches the bottom of the shale bed causes reversal of the combustion zone and drives same back thru the `bed to the top thereof, the direct drive combustion now consuming the coke deposited during the movement ofthe combustion zone downwardly thru the bed. It is during this phase of the operation wherein the direct burning combustion zone moves upwardly thru the bed that the gas flowing thru drill hole 16 is passed thru conduit 20 and drill hole 18 into the top of the shale bed in chimney 14 as retorting gas. During the inverse drive of the combustion zone downwardly thru chimney 12 by injection of air thru line 42 and well 22, produced oil in vaprous form is recovered thru line 44 along with combustion gas. During the next phase of the operation, the gas injected into the bottom of chimney 12 containing the hot spent shale picks up heat therefrom and leaves the top of the spent shale bed at a temperature approximately that of the hot shale (at least 800 F.). Since this gas is uesd in retorting the bed of shale in chimney 14 and some heat must be added to this gas to complete the production of oil from the shale in chimney 14, suiicient air is incorporated in the gas injected thru well 22 to propagate the direct drive of the combustion zone thru the residual coke on the shale in chimney 12. During this phase of the operation, spent retorting gas in the annulus of well 24 is recycled thru conduit 36 so as to provide a volume ratio of spent retorting gas to air in the range of 1:1 to 4:1. At the start of this phase of the operation, it is feasible to inject undiluted air to establish the direct drive of the combustion zone, after which the air may be mixed with recycle combustion gas (spent retorting gas) in the ratios disclosed, and it is feasible to also inject air intermittently at suicient concentration to periodically renew propagation of the combustion front thru the residual coke in chimney 12.

In order to control the temperature of the retorting gas prepared in chimney 12 for injection into chimney 14, a temperature sensing device 52 is positioned in line or conduit 20 to sense the temperature of the gas therein. When the temperature of the gas in line 20 tends to fall below about 850 F., suticient air is injected thru line 42 to provide an adequate concentration of O2 in the resulting gas to burn additional residual carbon in the spent shale in chimney 12. At times, it will be desirable to inject air without any injection of recycle gas from line 36 until the temperature of the gas in line 20 rises to some suitable level, such as 875-1000 F. After this temperature level is established in the retorting gas in line 20, recyle retorting gas is again introduced to well 22 from line 36 by operating the valve therein and this is either mixed with air to provide the specified ratio of recycle gas to air or it can be injected without any air until the temperature again tends to fall below 850, at which time the building up of the temperature in the foregoing manner may be repeated. Thus, it is feasible to continually or intermittently burn the residual carbon in the spent shale in chimney 12.

The first phase of the operation involving the production of oil from the shale in chimney 12 may be effected by initiating combustion in the top of the shale bed in any suitable manner and feeding air from line 44 thru drill hole 16 into the combustion zone so as to drive same downwardly thru the bed to the ybottom thereof. During this operation, it is essential to control the oxygen concentration in the injected gas so as to maintain the temperature in the range of about 900 to 1200 F. in order to form some coke on the spent shale which can be burned to provide additional heat during the second phase of the operation in which air and recycle combustion gas are fed thru well 22 and upwardly thru the hot spent shale in chimney 12. A convenient method of maintaining the temperature in this range comprises admixing combustion gas with the injected air and feeding the mixture thru line 44, with control of the volume ratio of combustion gas to air in the range of about 3:1 to 5:1. During production of oil by direct drive in this manner, liquid oil is produced in tunnel 26 and may be produced therefrom by running a tubing string with a pump on the lower end into well 22 as shown in well 24.

The third method of producing the broken shale in chimney 12 comprises injecting hot combustion gas at a temperature of at least 800, and preferably 850, thru line 44 so as to heat and release oil from the broken shale with production of the oil from tunnel 26 and well 22 by conventional pumping. Following the substantial completion of production of the shale with retorting gas, air is injected thru line 42 and passed thru well 22 and tunnel 26 into the bottom of the shale bed in chimney 12 to burn at least a portion of the carbon residue on the shale, and the resulting combustion gas is passed thru drill lhole 16, conduit 20, and drill hole 18 into chimney 14 as retorting gas in the sarne `manner as previously described. After a short period, some of the spent retorting gas in the annulus of well 24 is drawn off thru line 36 under the impetus of compressor 38 and mixed with air in well 22. Here again, it is feasible to continually or intermittently inject air into the gas passing into chimney 12 to provide hot retorting gas and the temperature of this retorting gas in line 20 may be controlled as described hereinbefore.

The process disclosed herein substantially avoids channeling due to convection currents and conserves heat. When an attempt is made to propagate a zone of heat vertically upwardly thru the shattered oil shale, natural thermal convection currents are set up in the broken shale due to temperature differences between the hot and cold gases which results in bypassing and channeling. This leaves unproduced oil in the chimney. The preferred embodiment of the invention avoids this by introducing hot retorting gases into the top of the first nuclear chimney and driving the hot zone downwardly. All of the disclosed embodiments of the invention drive the hot zone downwardly in the second chimney and avoid natural thermal convection currents and channeling.

Certain modifications of the invention will become apparet to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim:

1. A process for producing oil from first and second spacedapart explosion chimneys in an oil shale which comprises, in combination, the steps of:

(a) producing oil from said first chimney by heating the shale therein to a temperature of at least 800 F. by passing a zone of heat downwardly from the top section to the bottom section of said chimney under conditions leaving a hot residue containing sufficient coke to support in situ combustion;

(b) thereafter, passing a gas comprising air and recycled retorting gas upwardly thru the hot residue in said first chimney to burn said coke and extract heat from said residue, providing a hot retorting gas at a temperature of at least 800 F. as an efiiuent;

(c) passing hot retorting gas of step (b) downwardly thru the shale in said second chimney so as to produce liquid oil in the bottom thereof;

(d) separately recoveringr produced oil and eiuent gas from the bottom section of the chimney of step (c); and

(e) recycling a substantial portion of the recovered efiiuent gas of step (d) to step (b) as said recycled retorting gas.

2. The process of claim I1 wherein the shale in said first chimney is produced by inverse in situ combustion by initiating combustion in the top section thereof, feeding air upwardly thru the shale in said first chimney to the resulting combustion Zone so as to cause same to move downwardly to the bottom section of said first chimney, with produced oil being recovered from the top section thereof.

3. The process of claim 2 wherein the inverse burning combustion zone is reversed near the bottom of said first chimney and driven back toward the top of said chimney with injected air alone, and thereafter recycle gas is added to the air to provide a volume -ratio of recycle gas to air in the range of about 1:1 to 4:1.

4. The process of claim 1 wherein the concentration of air in the retorting gas of step (b) is maintained sufiiciently high to burn a substantial portion of said coke during a substantial portion of the operation in step (b).

5. The process of claim 4 wherein the volume ratio of recycle `gas to air in step (b) is maintained in the range of about 1:1 to 4:1.

6. The process of claim 1 wherein the temperature of the etiiuent retorting gas in step (b) is sensed and the air concentration in the injected gas is regulated in the range of 0 to 100 volume percent so as to maintain an eiuent temperature of at least 850 F.

7. The process of claim 1 wherein production in step (a) is effected by downward iiow of hot combustion gas at a temperature of at least 800 F. and oil is recovered from the bottom of said first chimney.

8. The process of claim 1 wherein production in step (a) is effected by downward direct drive combustion with a combustion gas-air volume ratio in the range of about 3:1 to 5:1.

9. The process of claim 1 wherein principally air is injected in the early phase of step (b) and principally recycled gas is injected in later phases with intermittent injection of air to increase efiiuent gas temperature.

10. The process of claim 1 wherein production in step (a) is effected by downward direct drive combustion.

References Cited UNITED STATES PATENTS 2,584,605 2/1952 Merriam et al. 166-11 2,780,449 2/ 1957 Fisher et al. 166-l1 3,001,775 9/1961 Allred 166-11 3,017,168 1/1962 Carr 166-11 X 3,044,545 7/1962 Tooke 166-11 3,163,215 12/1964 Stratton 166-11 X 3,316,020 4/1967 Bergstrom 166-11 X 3,342,257 9/ 1967 Jacobs et al.

OTHER REFERENCES Lombard, D. B., Recovering Oil From Shale With Nuclear Explosives, in J. Petroleum Technology, 15(8), August 1965, pp. 877-882.

CHARLES E. OCONNELL, Primary Examiner. I. A. CALVERT, Assistant Examiner.

U.S. C1. X.R. 16S-263, 272, 303 

